Production of yarns with varying twist



Jan. 11, 1966 w. e. PATERSON 3,228,181

PRODUCTION OF YARNS WITH VARYING TWIST Filed March 9, 1964 A tlorneys United States Patent 3,228,181 PRODUCTION OF YARNS WITH VARYING TWIST William Gilchrist Paterson, Croesyceiliog, Cwmbran, England, assignor to British Nylon Spinners Limited, Pontypool, England Filed Mar. 9, 1964, Ser. No. 350,361 Claims priority, application Great Britain, Mar. 22, 1963, 11,379/ 63 5 Claims. (Cl. 57-157) The invention concerns improvements in or relating to the production of yarns with varying twist.

It is already known that coherence of a bundle of filaments can be effected by imparting alternating S and Z twist to the bundle instead of the more conventional unidirectional twist. Processes are known in which such alternating twist is imparted by alternating contact between the bundle and the two opposing flanges of a rotating, reciprocated flanged traverse-guide, and by subjecting the bundle alternately to the action of two gas vortices of opposite direction.

We have now found a way in which alternating twist can be imparted, which is an improvement over the abovementioned processes, in that the twisting efiiciency is inherently better than either of such processes, and in that the apparatus required is simpler, needing no combination of rotational and reciprocating movements to be imparted to a single member and needing no special supply of gas, such as compressed air, to the machine. It is also more economical on the latter score.

According to the invention, a varying, e.g. alternating S and Z, twist is imparted to a filamentary structure by linearly advancing the structure across, and causing it to make intermittent contact with, at least one surface moving across the line of travel of said structure, said surface or surfaces having a high coefficient of friction with the structure. Conveniently, such intermittent contact may be made alternately with two surfaces moving in opposite directions. Such two surfaces can be comprised by two segments of an endless belt following a figure-of-eight path around two rollers or pulleys.

Alternatively, such surfaces can be comprised of the inner peripheral surfaces of two oppositely-rotating twisttubes, for instance such twist-tubes as are described and claimed in our US. Letters Patent No. 2,936,567.

In a presently preferred form of the invention, an alternating S and Z twist is imparted to a multifilament yarn by traversing the linearly advancing yarn in alternating contact with oppositely-moving segments of an endless band that is twisted to follow a figure-of-eight path around two rollers or pulleys, at least one of which is driven, the band having a surface, at least, composed of a material, such as neoprene, which has a high coeflicient of friction with the yarn.

The traversing may be effected by any convenient type of traverse mechanism, such as a reciprocating traverse mechanism, positioned either upstream or downstream of a crossed band; and sometimes the traverse mechanism may be positioned downstream, and be also employed, on its own downstream side, to traverse the alternately twisted yarn on to a wind-up package. If two oppositely-rotating twist-tubes are employed to impart an alternating twist, such twist-tubes may be mounted with their axes in staggered, parallel relationship to the mean line of travel of the yarn therethrough, and the yarn be reciprocated into alternating contact with the inner peripheral surfaces of each of the two twist-tubes by means of a rockable three-armed yarn-guiding member, the arms of the member bracketing the two twist-tubes, one arm on each side of the twist-tube assembly and one between the two twist-tubes.

The yarn must be held in firm contact with the surfaces moving in opposite directions, such as the twisted, crossed band; and this can simply be effected by passing it through guides so positioned on each side of the crossover point of the band that the yarn path is deflected through an angle, say between 45 and 90, where it passes over the band.

The material of the band or other yarn-contacting surface is also of importance to the efficiency of the twisting; and preferably the band in its entirely is made of polyurethane, neoprene or rubber, i.e. such material as will not only afford adequate twisting propensity but will also be suitable for fitting tightly on to the rollers or pulleys for lengthwise rotation. For optimum results, the band should have a shore A hardness less than The other two factors mainly influencing twisting efliciency in the preferred form of the invention are the relative speed of the band and the yarn, and the tension in the yarn before and after the points of twisting contact. As to the former, efiicient twisting is observed when the ratio of band speed to yarn speed is of the order of /2 or greater. As to the latter, the input tension should be low, say of the order of from 0.03 to 0.3 gram per denier; but the output tension, which may be the wind-up tension, may be as high as 1 gram per denier, for instance.

The period of alternation of S and Z twist in the yarn, if such alternating twist is that which is to be produced by the invention, is inversely proportional to the frequency of the traverse.

It is to be observed that the process of producing an alternating twist in a yarn is dependent on a cyclical change in the direction of twisting, both upstream and downstream of the twist-imparting agency. Such a stateof-afi'airs is to be contrasted with the equilibrium twist-direction conditions pertaining to false twisting.

Although, a belt, a band and two oppositely rotating twist-tubes have been referred to above as possible twistimparting agencies, there is no limitation of the invention thereto. For instance, contra-rotating discs can comprise the oppositely-rnoving surfaces for imparting twist. Further, the cross-section of a belt or a band does not have to be oblong; a square or a circular cross-section can be employed satisfactorily instead.

The varying, e.g. alternating S and Z, twist can be imparted according to the invention by intermittent contact between the yarn and at least one moving surface, rather than by alternating contact with oppositely-moving surfaces. In such a case, when using a crossed band as the twist-imparting agency, it is possible to lead the yarn in a direction perpendicular to the plane of linear figure-ofeight rotation of the crossed band, and to urged it intermittently into simultaneous contact with two segments of the band that are moving in opposite directions. Or, alternatively, it is possible to lead the yarn around and across one segment only of the crossed band in intermittent fashion. If a twist-tube of the type above referred to is employed for intermittent contact with the yarn, a pivoted, two-pronged yarn-guiding member may be used to guide the yarn diagonally through the bore of the twist-tube, such member being rocked to bring the yarn intermittently into, and out of, contact with both flared ends of the twist-tube.

The invention will now be described with reference to the accompanying drawings, in which FIGURE 1 is a diagram illustrating an endless crossed band for carrying out the presently preferred form of the invention for imparting alternating twists;

FIGURE 2 is a diagram illustrating a twist-tube assembly for imparting alternating twist;

FIGURE 3 is a diagram illustrating a single twist-tube for imparting alternating twist;

FIGURE 4 is a diagram illustrating an endless band for imparting intermittent twist;

FIGURE 5 is a diagram illustrating an endless crossed band for imparting intermittent twist.

In FIGURE 1, a crossed endless band 1 of rubber or of synthetic elastomeric material is revolved around pulleys 3, 5 by the eifect of rotary motion imparted to one of the pulleys. Positioned in line with, and on one side of, the cross-over point of the band is reciprocating traverse guide 7. Yarn Y is passed through guide 7', and thence is bent around the crossed band at the cross-over point, the angle through which the yarn path is bent being between 45 and 90. The yarn passes through another guide (not shown) downstream of the crossed band. The effect of the reciprocation of the traverse guide, as shown by the broken lines, is to cause the yarn to be brought alternately in contact with the oppositely-moving segments of the band, to impart an alternating twist to the yarn. I

In FIGURE 2, oppositely rotatable twist-tubes 9, 11 are mounted for rotation on parallel axes, one axis being laterally offset with respect to the other and the mean line of advance of the yarn Y being midway between said axes. The yarn is caused to be brought alternately in contact with the oppositely-moving peripheral surfaces of the twist-tubes, such surfaces having a high coeflicient of friction with the yarn, by a rockable three-armed yarnguiding member 13, having arms 15, 17 and 19 each bearing a yarn-guide.

When a single twist-tube is used-to impart alternating twist, as shown in FIGURE 3, the yarn Y is brought alternately in contact with opposite sides of the peripheral surface of each end of the twist-tube 9, the yarn passing diagonally through the twist-tube so that the instantly contacted sides at both ends are moving in the same direction. The alternating movement of the yarn is brought about by the action of swingable thread-guiding member 21 having two arms 23, 25 each bearing a yarn-guide.

FIGURES 4 and 5 illustrate two diife'rent ways of imparting intermittent twist. In FIGURE 4 an endless band 1 is revolved around pulleys 3, 5, each rotating in the same direction, by the effect of rotary motion imparted to one of the pulleys. A reciprocating thread-guide 7, moving in the vertical plane as shown by the broken lines, moves yarn Y intermittently into contact with the outer surface of endles band 1, such surface being composed of a material, such as rubber, having a high coeflicient of friction with the yarn. In FIGURE 5, as in FIGURE 1, the endless band 1 is crossed. In this case, however, instead of yarn Y being passed over and bent around the cross-over point of the band, it is passed within one loop of the figure-of-eight and is brought intermittently into contact with the inside surface of two oppositely-moving segments of the band near to the cross-over point. The yarn is thus rolled between the two surfaces to be twisted thereby. Reciprocating thread-guide 7 brings about this intermittent contact between the yarn and the segment surfaces, as shown by the broken lines.

In one example of the invention, in which alternating twist was imparted to the yarn by alternating contact with oppositely-moving segments of a crossed neoprene belt of 60 shore A hardness and of circular cross-section, 60 denier/20 filament yarn of polyhexarnethylene adipamide was passed at 1500 feet/minute across the belt which was travelling at 900' feet/minute and being rotated in figureof-eight formation around one driven on one idler pulley. The yarn was traversed at 60 cycles per minute by a traverse guide positioned upstream of the crossed belt, so as to make alternating contact with oppositely-moving segments of the belt. The yarn path was deflected through 45 around the crossed band. The input tension was 12 grams, and the output tension after alternate twisting was 60 grams, at which tension the yarn was wound up. The product was a stable alternating twist yarn with a twist cycle length of 300 inches, and an average twist value over half a twist cycle of 4.5 turns per inch.

Dependent on variations of the speed of traverse and of the ratio of belt speed to yarn speed, and on the nature of the belt material, average twist values of between 1 turn per inch and 5 turns per inch were also obtained in stable alternating twist yarns, according to the above exemplary process. The highest momentary twist value in the yarn, of 15 turns per inch, was obtained with a rubber belt of 50 shore A hardness travelling at 1500 feet/minute, the traverse frequency being 60 cycles per minute as before. The average twist in a half cycle was 5 turns per inch in that instance.

The varying twist according to the invention need not be alternating in direction, and may be unidirectional, varying in value above and below a mean twist. Thus, if a yarn of 10 turns per inch is passed in alternating contact with the oppositely-moving segments of a crossed band, the twist in the yarn may be caused to vary between, say Sand 15 turns per inch in the same direction as the original twist.

Varying twist may be applied .to a yarn at various stages of its processing. For instance, such twist, of alternating S and Z direction, may be applied to multifilament yarns, such as those of nylon, before or after they have been drawn. It is usually most advantageous to apply such alternating twist immediately prior to windingup after drawing, when the alternating twist takes the place of unidirectional twist imparted, say, by a ring spindle. There may be considerable productivity and yarn quality advantages in a Winding, as opposed to aringtwisting, form of wind-up. Particularly advantageous, owing to the low tension in the yarn as a result of the heat relaxing treatment, is the combination of a hot relaxing treatment, immediately after drawing, with the alternating twist process of the invention, such treatment and process being carried out on the yarn in that order. Yarn so produced and wound has very uniform physical characteristics, and the alternating twist applied to it affords adequate coherence of the filaments during subsequent processing, such as Warping, winding, sizing, weaving, knitting or braiding.

I claim.

1. A process for imparting a varying twist to a filamentary structure comprising the steps of (a) linearly advancing said structure along a path,

(b) intermittently contacting said linearly advancing structure on one side thereof with at least one surface moving across the path of said structure, said surface. or surfaces having a high coefiicient of friction with said structure, and

(c) winding up said structure with the varying twist thereby imparted to it.

. 2. A process according to claim 1 in which the varying twist is alternating in the S and Z directions.

3. A process according to claim 2 in which the surface or surfaces comprise two oppositely moving surfaces each of which contacts the filamentary structure alternately.

4. A process for imparting an alternating twist to a multifilament yarn comprising the steps of (a) linearly advancing the yarn along a path,

(b) alternately contacting said linearly advancing yarn on one side thereof with oppositely moving segments of a revolving crossed endless band having a surface 5 6 at least composed of a material having a high co- References Cited by the Examiner efficient of friction with the yarn, and UNITED STATES PATENTS c Windin u said am with the stable alternatin lwisttheibyfimpartgdtoit 2,957,302 10/1960 Lenk et a1. 57 -77.3

5. A process according to claim 4 in which the path of 5 2988867 6/1961 Quittner 57 157 the linearly advancing yarn is deflected through an angle of between 45 and 90 while the yarn is alternately con- MERVIN STEIN Pnmary Examiner tacted by said oppositely moving segments of said crossed D. E. WATKINS, Assistant Examiner. endless band. 

1. A PROCESS FOR IMPARTING A VARYING TWIST TO A FILAMENTARY STRUCTURE COMPRISING THE STEPS OF (A) LINEARLY ADVANCING SAID STRUCTURE ALONG A PARTH, (B) INTERMITTENTLY CONTACTING SAID LINERALY ADVANCING STRUCTURE ON ONE SIDE THEREOF WITH AT LEAST ONE SURFACE MOVING ACROSS THE PARTH OF SAID STRUCTURE, SAID SURFACE OR SURFACES HAVING A HIGH COEFFICIENT OF FRICTION WITH SAID STRUCTURE, AND (C) WINDING UP SAID STRUCTURE WITH THE VARYING TWIST THEREBY IMPARTED TO IT. 